cPanel backups now creating dirs and not .tar.gz files?

Just asked cPanel to perform a full backup on a hosting account. I was expecting (from previous experience) that it would create a single (large) .tar.gz file. Instead it created a backup directory with all the files, directories, etc. inside - all uncompressed/unzipped, plus a .tr.gz file with 0 bytes. Proof

I would have preferred the old .tar.gz file. Any reason why this changed?

Hang on - looks like I might be half way to answering my own question - I tried the full backup on another account of MUCH smaller size - and the tar.gz file was created as expected. The account (above) that I was backing up was huge. So perhaps for some reason backup dirs are created instead of .tar.gz backup files when the accounts are massive?